As people pay more and more attention to their health and healthy diet, many related products have been widely recognized and accepted. Wherein polyunsaturated fatty acid products play an important role in market. Raw materials as pharmaceuticals or dietary supplements or feed additives have a broader development and application prospect.
PUFA is a component of cell membrane. PUFA is an important basic substance for body metabolism, especially for infant brain development. PUFA mainly plays a role on physiological functions such as maintaining cell membrane fluidity, promoting cholesterol esterfication, reducing cholesterol and triglycerides levels, decreasing blood viscosity, and improving blood circulation and so on. Furthermore, PUFA can also have functions such as improving human thinking and enhancing memory. Lacking PUFA would result in many connate or acquired diseases. However, PUFA cannot be synthesized by the body itself. PUFA must be obtained from diet.
There are various kinds of PUFA including ω-3 PUFA, ω-6 PUFA, ω-9 PUFA, and other kinds of conjugated linoleic acid, such as α-Linolenic acid (ALA), eicosapentaenoic ester (EPA), docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), linoleic acid (LA), conjugated linoleic acid (CLA), γ-linolenic acid (GLA), arachidonic acid (AA) and so on. Wherein EPA and DHA representing ω-3 PUFA are known and acceptable to the public and obviously improve human thinking and enhance memory. Their molecular structures of polyunsaturated fatty acids are as follows.

Polyunsaturated fatty acids mainly derive from algae extract and marine oil, one of important sources comes from fish oil.
Liquid raw materials of polyunsaturated fatty acid product absorbed by the body mainly includes free-type polyunsaturated fatty acids, ethyl ester-type polyunsaturated fatty acids, glyceride-type polyunsaturated fatty acids. These raw materials have related functions and also have a series of deficiencies. First of all, these products exist in liquid form and have certain fishy smell. It would make some people have certain psychological resistance and consequently would not be accepted by the public. So it have some limitation in scope of uses. Secondly, absorption and utilization of some products are also not sufficient in the body, and then the bioavailability of some products is lower and so on.
Polyunsaturated fatty acid-calcium products can make up for the above deficiencies to a certain extent. First of all, polyunsaturated fatty acid-calcium products as a quality source of calcium can supplement calcium nutrition needed for the body. Besides it does not undermine effects on polyunsaturated fatty acids. Secondly, polyunsaturated fatty acid-calcium products exist in the form of free-flowing powder product, and consequently have broader application scope of polyunsaturated fatty acids. The products have no peculiar smell, good stability, and other advantages. The products can improve the bioavailability of polyunsaturated fatty acids for the body to some extent.
At present, processes of preparing polyunsaturated fatty acid-calcium products mainly include directly melting glyceride-type polyunsaturated fatty acids with calcium oxide or calcium hydroxide to obtain polyunsaturated fatty acid-calcium; or melting free-type polyunsaturated fatty acids with calcium oxide or calcium hydroxide to obtain polyunsaturated fatty acid-calcium; or firstly various of ester-type polyunsaturated fatty acids are saponified to obtain polyunsaturated fatty acid sodiums, and then perform an ion exchange of sodium and calcium to obtain polyunsaturated fatty acid-calcium products. But the above processes have some deficiencies.
One of processes is to directly perform a calcification of raw materials of calcium oxide or calcium hydroxide in a molten state with glyceride-type polyunsaturated fatty acids or free-type polyunsaturated fatty acids to obtain polyunsaturated fatty acid-calcium products. Firstly, polyunsaturated fatty acids are easy to cause oxidation, decomposition or polymerization and other destructive effects at the temperature because the reaction temperature is higher up to more than 200˜300° C. Secondly, calcium oxides or calcium hydroxides do not dissolve in a reaction system because of poor solubility. It could result in lower reaction degree, longer reaction time, lower reaction yield and other shortcomings, and then finally polyunsaturated fatty acid-calcium products have poorer quality.
Another process is to firstly perform a saponification of methyl ester-type, ethyl ester-type or glyceride-type polyunsaturated fatty acids with liquid alkali to obtain polyunsaturated fatty acid-sodium, or then acidify to obtain polyunsaturated fatty acids; and afterwards react polyunsaturated fatty acid sodium or free-type polyunsaturated fatty acid with various of calcium compounds to obtain polyunsaturated fatty acid-calcium, wherein the calcium compounds include calcium oxide, calcium hydroxide, calcium acetate, calcium lactate, calcium chloride. But the process is more complicated. Wherein the first step is to perform a saponification, a large number of polyunsaturated fatty acids are destroyed under a strong alkaline condition due to addition of a large amount of liquid alkali. It could make color of intermediate and final products darker and make product quality lower. Secondly, it could decrease reaction degree and reduce product yield because calcium oxide and calcium hydroxide are almost insoluble in water or various of organic solvents or various of polyunsaturated fatty acids in a reaction system. Besides, the process is more complicated because the process overall includes saponification, pickling, washing, recovery of solvents, calcification, filtration, drying, grinding and other processes. And the quality of final products is poor, and has lower yield and the process could produce a large amount of wastewater.
There have been a series of methods of preparing for polyunsaturated fatty acid-calcium products.
U.S. Pat. No. 5,382,678 directly performs a calcification of glyceride-type fish oil polyunsaturated fatty acid with calcium oxide or calcium hydroxide at 250° C. The process is not sufficient and lower yield, although selecting glyceride-type polyunsaturated fatty acids with higher boiling point and slightly better oxidation resistance could overcome impact of high temperature on raw materials to a certain extent, the content of glyceride-type fish oil in the final product is merely more than 10%, and the product is too stickiness to form a free-flowing powder product.
Patents U.S. 60/724,644, U.S. 60/775,664 describe a process of direct performing a calcification of calcium oxide or calcium hydroxide with free-type polyunsaturated fatty acids or various esters-type of polyunsaturated fatty acids. But the process has higher reaction temperature, lower reaction degree and poor product quality. Another process is to perform a saponification of various of ester-type polyunsaturated fatty acids to obtain polyunsaturated acid sodium firstly, and then to perform ion exchange to obtain a polyunsaturated acid-calcium. But the process has longer route, produces more wastewater and lower yield.
U.S. patent Ser. No. 09/675,745 relates to a process of heating polyunsaturated fatty acid firstly, then adding a hydrate of calcium oxide slowly, finally evaporating water and other procedures. But the process is carried out in a special environment, and has complicated, lower reaction degree, poor product quality, because calcium oxide is insoluble in water.
Patent CN1270160 describes a process of preparing free-type fatty acid by saponification and acidification in turn, and then reacting purified free-type fatty acid with calcium hydroxide to obtain polyunsaturated fatty acid-calcium products. But the process has longer reaction time, lower reaction degree, lower yield, because calcium oxide is insoluble in water.
Patent CN102417444 describes a process of directly reacting fatty acids with calcium hydroxide or calcium oxide to obtain fatty acid-calcium. Wherein the process uses a continuous mode to improve reaction yield by continuous precipitation of fatty acid-calcium mode, and finally obtains 80˜85% of yield. But the process produces a large amount of wastewater, and has lower product purity.
Patents CN1752064, CN1685921 describes a process of performing a saponification of fatty acids with liquid alkal to obtain fatty acid sodium, and then performing an ion exchange with calcium chloride to obtain fatty acid-calcium products. But the process route is complicated, and has 80% lower yield and produces a large number of chlorine-containing wastewater, and then results in a serious pollution to environment.
On the whole, most of preparation methods of polyunsaturated fatty acid-calcium products in the prior art mainly have at least one of the following problems: 1) insoluble calcium oxide or calcium hydroxide resulting in lower reaction degree, longer reaction time, lower yield and other problems because of using calcium oxide or calcium hydroxide as raw materials; 2) uses of high temperature condition or liquid alkali resulting in a large amount of polyunsaturated fatty acid damaged and poor product quality.
Generally speaking, main materials of preparing for polyunsaturated fatty acid-calcium products are polyunsaturated fatty acids and calcium compounds. But polyunsaturated fatty acids including free-type polyunsaturated fatty acids and esters-type polyunsaturated fatty acids are not stable because these compounds contain more double bond groups. Wherein free-type polyunsaturated fatty acids have a lower boiling point and the least oxidation resistance; methyl ester-type or ethyl ester-type polyunsaturated fatty acids take second place; and glyceride-type polyunsaturated fatty acids with the highest boiling point are relatively stable. But glyceride-type polyunsaturated fatty acid is prone to polymerization to form polymers at more than 260° C. Besides, polyunsaturated fatty acids are prone to produce structure damaged and curing matter state with darker color appearance because polyunsaturated fatty acids are more sensitive to strong acid or strong alkali environment.
There are some limitation for selection of calcium compounds. Calcium oxide or calcium hydroxide is a common use. Compounds having a certain basicity are easy to react with polyunsaturated fatty acids in theory. However, polyunsaturated fatty acids and calcium cannot fully contact together because of heterogeneous reaction of liquid and solid, and produce low reaction degree because of insolubility of calcium oxide or calcium hydroxide itself. Even polyunsaturated fatty acid-calcium product encases calcium compounds and thereby inhibit continuation reaction because of production of insoluble polyunsaturated fatty acid-calcium product. Eventually it would lead to a long reaction time, lower content of product.
In addition, water-soluble calcium compound is relatively little, the main reason is to obtain polyunsaturated fatty acid sodium by saponification of polyunsaturated fatty acid by using a large number of liquid alkali and water in the process. So it would make polyunsaturated fatty acid material destroyed, decrease product quality and produce a large amount of wastewater.